Coffee filtering

ABSTRACT

A coffee filtering system having a single percolation, using a compressed coffee tablet in a closely fitting holder.

United States Patent [1 1 Molenaar et al.

[ Apr. 2, 1974 COFFEE FILTERING [75] inventors: Albert MeijlomMolenaanTerkaple;

' Melle Veenstra, Joure, both of Netherlands [22] Filed: Dec. 15,197]

[21] Appl. No.1 208,098

{301' Foreign Application Priority Data [56] References Cited UNITEDSTATES PATENTS l,636,l79 7/1927 Gchlcrt 99/306 1,680,5[9 8/]928 Houck99/306 1,964,]5] 6/1934 Guntrup 99/306 3,139,344 6/]964 Wcisman 99/295Primary ExaminerRobcrt W. Jenkins Attorney, Agent, or Firm-Baldwin,Egan, Walling Fetzer [57] ABSTRACT Sept. 7, I971 Netherlands 71 l2303coffee filtering System having a Single percolation, [52] U S Cl 99/29599/306 using a compressed coffee tablet in a closely fitting h- 51 1Int. Cl A23f [58] Field of Search 99/298, 292, 293, 295, 5 Claims, 3Drawing Figures i n I, T)

applying this filtering method and to a pressed tablet of ground coffeesuitable for applying this method, while use may be made of such acoffee filter.

The object of the'invention is to provide an improved coffee filteringmethod with a single filtration, with a coffee brew of very high qualityand a high extraction yield and which is particularly also suitable forapplication in a disposable filter system.

To this end it is proposed to apply a compressed tablet of roasted andground coffee, the coffee tablet being kept in contact-with preheatedwater for moistening the coffee tablet during a first period withoutpercolation of water, afterwhich the extraction of the coffee takesplace during a second period while the desired quantity of waterpercolates through the ground coffee.

SUMMARY OF THE INVENTION By employing a pressed coffee tablet andopposing 1 the percolation of water through-the tablet for a certaintime, there is time for the water to moisten the coffee, during whichsoluble constituents of the coffee are already released. After that,with. the percolation of the water, the extraction period of the coffeebegins. A coffee brew prepared in this manner appears to haveparticularly good flavor properties. A compressed tablet guarantees inall conditions an even filtering, while a brewing time within narrowlimits can be maintained. Without the inconvenience of dusting, use'canbe made of very finely ground coffee, which will improve the quality ofthe brew.

, It has appeared that good results are obtained if the first periodtakes about one quarter of the total brewing time and the second periodthe remaining three quarters of this brewing time, the total brewingtime being between 2 and 6 minutes, moreparticularly between 4 and 5minutes. The latter case corresponds with a moistening period of about 1minute.

According to the invention, a coffee filter for applying thefilteringmethod of the present invention has a holder for ground coffee withfilter bottom, which holder is so constructed that on top of it areservoir for a certain quantity of preheated water can be arranged andwhich can be suitably positioned above a collecting basin for thecoffeebrew, the holder for ground coffee being adapted to receive andembrace a compressed tablet ofroasted and ground coffee. On account ofthe fact that the coffee tablet is embraced in the holder, it isprevented that poured water oozes between the wall of the holder andthe-tablet without taking part in the moistening and extraction of thecoffee, while owing to the density of the tablet the water is stoppedduring the moistening time. Although the embrace of the coffee tablet ina given place is sufficient to prevent oozing of water, it has appearedto be efficient to construct the holder in such a manner that a coffeetablet is clamped over a slight height along the lower edge of theperiphery and is kept spaced from the filter bottom. Owing to this thetablet can freely expand on all sides, except for the embraced portionof slight height. During the moistening phase the coffee brew swells andthe tablet disintegrates. To receive the expanding coffee brew theholder for ground coffee is constructed with approximately three timesthe volume of the compressed coffee tablet.

It is observed that in dependence on the type of coffee used and theexpansion thereof a larger or smaller volume of the holder can be used.If the holder is too small the brew does not sufficiently disintegrateand the oozing of the water is hampered while in case of too large avolume all the brew is not sufficiently extracted.

To promote disintegration the tablet is kept spaced from the filterbottom.

To insure a correct and accurate brewing time the percolating time ofthe water is preferably determined by the coffee tablet itself and notfor instance by the filter element arranged therebelow. Owing to the useof pre-compressed coffee a much coarser filter bottom than usual can beapplied, the only requirement being that the pore size is justsufficiently small to prevent passage of the swollen moistened coffeeparticles almost completely. To obtain a good moistening of the coffeetablet and to prevent the swollen coffee brew from floating in the waterreservoir, there is preferably arranged between the water reservoir andthe coffee holder a grid having openings narrowing towards the interiorof the coffee holder, the smallest opening being in the order of 0.2-0.5mm. Gas .present in the extraction chamber must be able to escape. Topromote the gas discharge, steps as defined herebelow can betaken.

The invention will be elucidated with reference to the drawing showingsome embodiments of a coffee filter.

BRIEF DESCRIPTION OF THE DRAWING In this drawing:

FIG. 1 is a vertical section of a coffee filter having a water reservoiraccording to the invention;

FIG. 2 is a top view of the coffee holder of FIG. I; and Y FIG. 3 issubstantially a vertical section of another construction of a coffeefilter.

FIG. 1 shows a coffee tablet 1 received in a holder 2 for ground coffee,said holder being provided at the bottom with a filter bottom 3. Thecoffee tablet l is retained in the holder 2 by lugs 4. Above the holderthere is a grid 5, at the bottom of a water reservoir 6. The lugs 4 arealso attached thereto.

DESCRIPTION OF PREFERRED EMBODIMENT The coffee tablet 1 has the shapeof, at least at the bottom, a substantially fiat disc and is fittinglyarranged along the lower edge in a continuous edge 7 in the tabletholder 2 in such a manner that no water can pass along the periphery ofthe tablet. The lower face of the coffee tablet is spaced some distance(0.5-2 mm) from the filter element 3, which bears on a bearing cross 8.

The upper face of the tablet may be profiled for a better control of themoistening phase.

The tablet holder extends conically upwardly from the support edge 7, sothat the tablet has at least 1-2 mm space on the top to expand radially.Contiguous to the wall of this ex-traction chamber there is on the top aslightly upwardly inclined wall 9 having five radially extendingrecesses 10. The wall 9 has on the lower side five Wings 11 having astepped configuration on the lower side for centering the coffee filteron a cup. The wall 9 extends into an upwardly diverging wall 12 withsnapping lugs 13. The wall of the water reservoir 6 bears against thewall 12 and is retained by the lugs 13.

1n the wall of the water reservoir there are a number of vertical slots14 extending to a trapped portion 15. The bottom of the water reservoir6 with grid is slightly conical in downward direction. Gases and vaporswhich cannot easily escape through the small holes in the grid 5 deflectlaterally via the recesses 10, the space around the trapped portion 15and the slots 14. A number of stacking lugs 16 are arranged on the innerwall of the water reservoir. I

The coffee tablet is prepared by compression of ground and roastedcoffee having a grinding size division of:

13 percent 0.5 mm

56 percent 0.5 and 0.315 mm 18 percent 0.315 and 0.16 mm 7 percent 0.16and 0.10 mm 6 percent 0.10 mm To prevent disintegration of the tableowing to internal pressure build-up through released CO the coffee to becompressed may maximally contain about 0.3 percent by weight of COBesides, the CO content may not drop below 0.15 percent by weight toprevent too rapid oxidative decay of the coffee. The compression of thecoffee takes place at the lowest possible temperature, maximally 30 C.It has appeared that when compressing, possibly with an inert gas, at apressure of 200-750 kg/cm dependent on the coffee type applied, asuitable filter tablet with desired moistening and extraction time isobtained if the tablets are compressed with an average height-diameterratio between 1:4 and 1:8. With such a tablet an extraction yieldbetween 20 and 30 percent can be obtained if the water-cofiee ratioranges between 30 and 10. Thus, for example, with a water-coffee ratiobetween 20 and 14 and a height-diameter ratio of the tablet of 1:6 anextraction yield between 22 and 26 percent was obtained. If use is madeof water having a temperature between 80 and 100 C a brew of the desiredconcentration and of sufficiently high temperature can be obtained ifthe narrow ranges of moistening and extraction time are taken intoaccount. The coffee brew cannot be adversely influenced by precedinghandlings with the coffee filter. In a filter with loose coffee thecoffee easily sags to one side, as a result of which the filtration isnot optimal.

For a normal cup of coffee about 140 cm hot water is poured in the waterreservoir 6, the grid 5 insuring a good distribution of the water overthe tablet to be moistened. The total volume of the extraction chamberin the tablet holder 2 is, dependent on the properties of the brew,about three times the volume of the coffee table 1, in such a mannerthat the swollen brew fills the space almost completely. If the water ispoured on, the coffee tablet initially prevents the water frompercolating, while the coffee particles swell owing to the moistening.About after one minute the percolation of water starts.

The openings in the grid 5 are slightly funnel-shaped. The grid containsat least 50 small holes having a diameter of maximally 0.5 mm. Thedimensions are such that the coffee in the water reservoir 6 is almostcompletely prevented from floating. By keeping the narrowest portion ofthe openings on the tablet side of the grid, loosened coffee partieswhich possibly come into the openings and which expand therein whenmoistened, will float in the water and will not clog the grid. Since thefine, ground coffee is compressed, almost no loose coffee particles willreach the filter bottom. Only after the moistening phase is therequestion of separate coffee particles, but these particles havemeanwhile increased to three times their initial volume, so that a muchcoarser filter bottom than is necessary for loose coffee of the samegrinding fineness can be applied. I has appeared that the material usedfor tea bags is par ticularly suitable to serve as a filter bottom. Thissocalled heat-scalable tea bag paper of 17 g/m is for example marketedby Messrs. Bollor in France (type 1,000 K T) or Crompton in GreatBritain. By employing such a relatively coarse filter bottom thepercolating or extraction time is mainly determined by the coffee tabletand the coffee particles, as well as the shape of the tablet holder andnot by the filter bottom.

The coffee filter shown in FIG. 3, having a basketshaped extractionchamber, is provided with a coffee tablet l in the tablet holder 2',which is provided in the water reservoir 6. This water reservoir isprovided with a continuous edge 7', against which the coffee tabletbears sealingly. The tablet holder is provided with lugs 4 for retainingthe coffee tablet, while the wall extends slightly conically and isprovided with longitudinal slots having a maximum width of 0.2 mm. Thispart serves as a grid 5. The tablet holder forms part of the waterreservoir 6', which reservoir has a trapped, conical wall, with stackinglugs 17 for stacking with another coffee holder and an internal edge 18which determines the water level in the example 140 cm". It is observedthat in this example the tablet has a diameter of 44 mm and an averageheight of 8 mm, while the total height of the tablet holder is 23 mm.

It has appeared that a compressed tablet having a diameter of 44 mm evenshows a diameter increase of about 1 mm within 24 hours aftercompression. By placing the tablet directly after compression in thecontinuous edge 7 a very good water sealing along the lower edge of thetablet is obtained, partly owing to this expansion. The reservoir isprovided with an annular pilot surface 19, with which the filter elementcan be centered on a coffee cup, while in the annular pilot surfacethere are a few radial slots not shown for venting the coffee cup. Thewater reservoir is closed on the top by a possibly transparent cover 20having an outer annular pilot surface 21, with which the cover iscentered on the water reservoir and an inner annular pilot surface 22,between which, in the reverse position of the cover, the lower side ofthe filter can come to rest after use, so that the cover serves as asaucer.

On top of the coffee holder 2' there is provided a cap 23 partlyextending over the slots in the grid 5. Below the edge of this cap anair cushion is maintained, so that when the water is poured on, theupper ends of the grid slots remain active for venting and for the gasdischarge. The top of the coffee holder has an insert 24 to reduce thecentral space at the top of the coffee holder. lf ground coffee can alsodeposit there, it appears that it is less or hardly extracted. Owing tothe different shape of the coffee holder and the position of the gridslots the filter shown in FIG. 3 provides a less bitter, lighter flavorof the brew than the filter shown in F 1G. 1, in which the ground coffeeis almost completely vertically percolated.

The water reservoir and the tablet holder may be manufactured byinjection molding of polystyrene 466 i of B.A.S.F., for instance with awall thickness of 0.6 mm. Of course also different materials aresuitable, provided they resist water of 98 C. The filter assemblyaccording to the invention isvery well suitable for a disposablepacking.

It is observed that the invented method and the filter applied can alsobe used for making beverages other than coffee, for instance, tea, cocoaor the like. The compressed tablet may also comprise additives, likesugar or milk powder What is claimed is:

'1. A coffee filter comprising a holder for ground coffee, said holderhaving a filter bottom, a reservoir mounted on the top of said holderand adapted to receive a certain quantity of preheated water, saidfilter being adapted to be positioned above a collecting basin for thecoffee brew, said holder having means adapted to receive and closelyembrace a pressed tablet of roasted and ground coffee in a liquid-tightperipheral relation therewith effective to prevent any liquid fromflowing between the edge of said tablet and the holder.

2. A coffee filter according to claim 1, wherein the last mentionedmeans includes means operable for holding a coffee tablet at a slightheight above the lower edgeof the periphery of said holder and is keptspaced from said filter bottom.

3. A coffee filter according to claim 1 characterized in that the holderfor ground coffee has approximately three times the volume of thepressed coffee tablet.

4. A coffee filter according to claim 1, characterized in that saidfilter bottom has such a porosity that waterswollen coffee particles cannot precisely pass.

5. A coffee filter according to claim 1, characterized in that thecoffee holder is separated from the water reservoir by a grid havingopenings of which the smallest size is in the order of magnitude of0.2-0.5 mm.

1. A coffee filter comprising a holder for ground coffee, said holderhaving a filter bottom, a reservoir mounted on the top of said holderand adapted to receive a certain quantity of preheated water, saidfilter being adapted to be positioned above a collecting basin for thecoffee brew, said holder having means adapted to receive and closelyembrace a pressed tablet of roasted and ground coffee in a liquid-tightperipheral relation therewith effective to prevent any liquid fromflowing between the edge of said tablet and the holder.
 2. A coffeefilter according to claim 1, wherein the last mentioned means includesmeans operable for holding a coffee tablet at a slight height above thelower edge of the periphEry of said holder and is kept spaced from saidfilter bottom.
 3. A coffee filter according to claim 1 characterized inthat the holder for ground coffee has approximately three times thevolume of the pressed coffee tablet.
 4. A coffee filter according toclaim 1, characterized in that said filter bottom has such a porositythat water-swollen coffee particles can not precisely pass.
 5. A coffeefilter according to claim 1, characterized in that the coffee holder isseparated from the water reservoir by a grid having openings of whichthe smallest size is in the order of magnitude of 0.2-0.5 mm.